The prior art provides several mechanical devices which have many moving parts to find the center of a workpiece. Centering devices having multiple parts are described in the following United States patents: U.S. Pat. No. 6,243,963 B1; U.S. Pat. No. 6,158,137; U.S. Pat. No. 5,437,105; U.S. Pat. No. 1,309,930; U.S. Pat. No. 202,180 and others. These devices have many moving parts, and they are not suitable for dirty dusty wet environments. One piece devices and methods for finding the center of a workpiece are described in the following United States patents: U.S. Pat. No. 6,311,408 B1; U.S. Pat. No. 5,090,129; U.S. Pat. No. 2,764,818; U.S. Des. 399,769 and others. These devices are limited by their length to smaller workpieces.
Thus it is desirable to provide a simple one piece device for finding the center of any size workpiece. The present invention provides a one piece centering ruler, which may be used with a marking utensil, such as a pencil for finding the center of any size workpiece.